1. Technical Field
The present invention relates to a recording method for an optical disk and an optical disk recording reproduction device, and has an object to prevent degradation of recording quality by correcting spherical aberration.
2. Background Art
An optical disk, such as CD-R (recordable CD), DVD±R (recordable DVD), BD-R (write-once type Blu-ray Disc), or the like, has a structure that a recording layer and a reflective layer (and a protection layer as needed) are formed on one surface of an optically transparent disk-shaped substrate. Furthermore, spiral or concentric grooves called as grooves are formed on the surface of the substrate on which the recording layer and the reflective layer are formed, and a projecting portion called as a land is formed between neighboring grooves. With respect to the optical disk as described above, the recording layer on a groove is irradiated with a recording laser beam to form pits, thereby performing recording. The length of the pit, the length of the portion between the pits (hereinafter referred to as a space) and the arrangement of the pits are readout by applying a reproduction laser beam and detecting a reflective light as a reproduction signal, thereby performing reproduction.
With respect to the optical disk as described above, the recording layer is irradiated through an optically transparent layer with the recording laser beam and the reproducing laser beam. Here, in the case of CD-R or DVD±R, the recording layer and the reflective layer are successively formed in that order on the optically transparent disk-shaped substrate (the thickness is equal to 1.2 mm for CD-R and 0.6 mm for DVD±R), and thus the optically transparent disk-shaped substrate corresponds to the optically transparent layer. In the case of BD-R, the reflective layer and the recording layer are successively formed in that order on the optical transparent disk-shaped substrate having a thickness of 1.1 mm, and a transparent cover layer having a thickness of 0.1 mm is formed on the recording layer. Thus, the transparent cover layer corresponds to the optically transparent layer.
In the optical disk as described above, heat is generated when the recording layer is irradiated with the recording laser beam to form the pits. When the generation of this heat is excessive, the shape of the pits may be deformed to a shape different from the normal shape. The deformation of the pits has hitherto caused degradation of recording quality such as a jitter characteristic, etc., for example. In order to prevent the deformation of the pits, the power of the recording laser beam is adjusted. The power adjustment of the recording laser beam is executed as follows.
First, a test recording is executed on an output proofing area (an area called as PCA for DVD-R, for example) at the inner peripheral side of a data record region of the optical disk while the power of the recording laser beam is varied. Subsequently, among the results of this test recording, a result representing excellent recording quality is selected, and is calculated to be regarded as an optimum recording output. Subsequently, recording is executed on the data record region of the optical disk by the recording laser beam having the optimum recording power obtained by the above calculation.
However, the recording sensitivity of the recording layer of the optical disk is not fixed, but varies within each individual disk as well as among individual disks due to the production condition or the like in some cases. In the optical disk as described above, the optimum power of the recording laser beam varies, and thus when the recording is executed while the power of the laser beam is fixed to the power calculated according to the above method, there occurs a portion at which the optimum recording quality cannot be obtained. In view of the foregoing problem, as disclosed in JP-A-2003-263740, for example, a method of detecting a recording state after recording into a data area and correcting the power of the recording laser beam on the basis of the detection result has been proposed.
Furthermore, with respect to the recording of the optical disk, degradation of the recording quality occurs due to warp of the optical disk, variation in thickness of the optically transparent layer, a manufacturing error of tilt of lenses such as an objective lens, etc. at a pickup portion of an optical disk recording reproduction device, etc. For example, with respect to the variation in thickness of the optically transparent layer, there is a problem in that spherical aberration occurs in the spot of a recording laser beam or reproducing laser beam and thus the power of the recording laser beam varies, thereby disturbing the pit shape and degrading the recording quality as a result. Therefore, as disclosed in JP-A-2004-103093, there has been proposed a method of correcting the spherical aberration by using aberration correcting means provided to the optical disk recording reproduction device. Furthermore, the power of the recording laser beam changes due to a correction of aberration, and thus there has been proposed a method of correcting spherical aberration and then correcting the power of the recording laser beam as disclosed in JP-A-2003-109239.
Patent Document 1 JP-A-2003-263740
Patent Document 2 JP-A-2004-103093
Patent Document 3 JP-A-2003-109239